Human death in persons infected with SARS-CoV-2 (the virus responsible for the covid-19 pandemic) is caused by barriers dysfunction (i.e. in the pulmonary system). Angiotensin- converting enzyme 2 (ACE2) has been identified as a functional receptor of SARS-CoV-2, similarly to other coronaviruses. Surface expression of ACE2 protein was found on lung alveolar epithelial cells and enterocytes of the small intestine. In brain, ACE2 is expressed on endothelial cells, a major component of blood-brain barrier (BBB). We propose to perform a series of studies to assess the impact of SARS-CoV-2 spike protein on BBB function in the presence of cocaine as an extension of our funded research on psychostimulants and the CXCL12/CXCR4 chemokine system. First, a comprehensive series of experiments on the impact of SARS-CoV-2 spike protein in the presence and absence of cocaine on brain microvascular endothelial cells will be performed in vitro to inform on the cellular and molecular mechanism involved in altered BBB function. Included in the analysis will be measurements of cytosolic Ca2+ levels, mitochondrial reactive oxygen species, tight junctions and cytoskeletal proteins. Second, integrated fluorescence microscopy will be used to visualize and quantify changes in BBB permeability in real time in awake rats after exposure to SARS-CoV-2 spike protein. The impact of acute and chronic administration of cocaine on BBB function in the setting of SARS-CoV-2 spike protein will be determined. Finally, brain regions from rats exposed to cocaine and the spike protein will be examined for levels of pro-inflammatory cytokines and chemokines. Taken together, this series of experiments will provide novel information about the effect of the spike protein on BBB function and neuroinflammation, and its potential interactions with cocaine. We hypothesize that chronic cocaine exposure will exacerbate the negative impact of SARS-CoV-2 spike protein on BBB integrity and increase pro-inflammatory mediators in the CNS. These studies will provide the necessary groundwork to embark on a larger study of the impact of SARS-CoV-2 on cocaine behaviors and toxicities.